Rechargeable batteries are used to power a large number of different portable electronic devices. Presently, lithium-based battery technologies, such as lithium-ion, are very popular due to their superior energy storage capacity compared to earlier battery types such as nickel-based batteries (e.g. nickel-cadmium, nickel metal hydride). The higher energy storage density of lithium-based batteries has facilitated smaller and lower weight portable systems.
However, lithium-based battery technologies, while outperforming nickel-based battery technologies under nominal conditions, fall behind under some conditions. In particular, in very cold temperatures lithium-based systems are, in some applications, unable to deliver power at a rate required by the portable device they are powering, particularly portable devices that can have high current periods, such as portable two-way radio devices. In cases where operation is critical, it is necessary that a battery technology be able to deliver power to its host device.
Accordingly, there is a need for a method and apparatus for allowing utilization of a high energy density battery technology when it is below its operating temperature.
Those skilled in the field of the present disclosure will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. The details of well-known elements, structure, or processes that would be necessary to practice the embodiments, and that would be well known to those of skill in the art, are not necessarily shown and should be assumed to be present unless otherwise indicated.